Communication system



Nov. 2, 1943. 1.. H. ALLEN COMMUNICATION SYSTEM Filed Jan. 12, 1942 2 Sheets-Sheet l znzk vhm QQQM 20.0

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ing key l5 and this by causing the operation of relay I4 will release the holding relay l9 so that the holding circuit is now restored to its normal position.

When an emergency arises, the attendant at the control station 8 will be advised of it by an incoming call which will be answered by operating the answering key l5. Then the attendant will immediately establish a connection to a selected number of other subscriber stations, by operating the call key 23. This will connect his telephone line to the conductors 2| and 22 and talking current will be supplied through the windings of relay 23. Relay 23 will operate and through its right-hand tacts cause the operation of relay 24. Relay 23 armature and front con- I tube will break down and cause a current flow will also place ground on conductor 25 so 't'hat if the control station attendant now operates theringing key 26, ground will be extended back over conductor 21 to cause the operation of relay 28. Through its armature 4 and front contact relay 28 connects battery to the winding of relay 30 thus causing its operation. Relay 30 places ground on a number of conductors each going to the winding of a relay such as 32 in each of the circuits individual to the selected telephone stations which are called on this emergency circuit. Relay 32' in the left-hand called station circuit No. 1 leading to substation 33 will thus be operated and the connection from the substation 33 leading normally through the .upper armatures and back contacts of relay 32' to the connector andline finder multiples will be If the subscriber on station 33 is-involved in an established connection, this connection will be immediately interrupted. At the same time relay 28 connects battery which is characterized by a super imposed ringing current from the source 34, on to the lower winding of relay -thence over the back contact and middle upper armature of relay 35, the front contact and middle upper armature of relay 32 over the loop of the subscriber substation 33, the upper outer armature and front contact of relay 32,'the upper outer armature and back contact of relay 35 to ground. The establishment of this circuit causes the operation of relay35 which thereupon looks through its upper "winding, its front contact and inner upper armature of relay'32 to ground. The subscriber at substation 33 is now supplied with talking current through the windings of relay 36 and is connected in a conversational circuit to the 'calling control substation through the condensers 31v and 38. When relay 36 operates ground is placed on conductor'39 leading to the lower armature of relay 32 so that relay 32 will remain locked under the control of substation 33 even after relay 3!] under control of substation 8 is allowed to release.

If the substation 33 isidle, then the current supplied over the front contacts of relay 23 from the source of ringing current 34 will result in the ringingof this substation. 'When the substation answers relay 35 will respond and thus connect the substation to the conference circuit. V Upon the operation of relay 30 hereinbefore described a circuit is established from battery,

.front' contact and armature I of relay 33, re-

through the resistance 43 to ground. Through the condensers 46 and 41 bridged across the resistance 43, a tone caused by the intermittent currentflow'through resistance 43 and the harmonics of the ringing current source is connected across the conductors 2| and 22 comprising the conference circuit so that the subscriber at ceiverhook or momentarily release the call key 23 so" thatrelay 23 releases. Upon the release of this relay, a circuit is established from ground through the left-hand armature and back contact of relay 23, armature 'I and front contact of relay 42, the n'ormal contacts of armature 3 of relay 48; winding of relay 48 to battery. Re-

lay 43-operates and locks through its armature 3 to ground over the front contact and arma- 'and front contact to the winding of the off-normal relay 24 in parallel with the ground supplied by th'e front contact and right-hand armature of relay 23. Relay 42 will release as soon as relay 23 is operated again since ground will be extended from the left-hand armature and front contact of relay 23 over armature l and front contact- 9f relay' 48 to short-circuit the winding of relay 42. Upon the release of relay 42, relay 48 releases and thus the'tone circuit is disconnected f ro m the conference circuit.

'Should thefcontrol station attendant wish to connect tone to-the conference circuit again, he

may operate his ringing key 26 whereby the start relay 30 will againl'be momentarily operated to cause the operation of relay 42 in the manner hereinbefore described.

,7 In case the 'call'is' abandoned before the attendant has released the tone and all of the called subscribers with the. exception of the control station operator hang up, then relay '49 will be released and'will' extend ground I through its armature and back contact and over the armature 2 and front contact of relay 48 to cause the short circuit and release of relay 42.

In this manner therefore all of the substations which aresel'ected for thisvservice will be called in. Itshould be noted that in Fig.3 six called station. ci'rcuits are shown Ofindicated but this invention-is not limited to this number.

When the conference vhas terminated each of the substation lines involved lwill be restored to 1135. normal. circuit. when the subscriber thereon opens his substation loop and allows the associated talking current feed relay 38 to release. The control substation may be released by replacing the handset on the cradle or by releasing the call key 20. Thereup on relay 23will-be released causing the return to normal of the offnormal relay 24. Relay 28 of course releases as soon as the ringing key 26 is released. It will thus be understood that the conference circuit may be maintained in any one or more substations and is not completely released until all substations have hung up.

The operator at the control station may ring and rering at will. As each substation answers the call to the conference, its lamp 411 will light up as a signal that that substation is in on the conference connection. If all of the substations do not immediately respond the operator at the control station 8 may rering by operating the ringing key 26. Those stations which have answered will not be alfected as the application of ringing current by the relay 28 is ineffective but any station which has not answered will be run-g again.

It should be noted that a plurality of control stations may be provided. Thus a control station 52 coming from a line denoted by its tip and ring conductors 50 and may have control over the conductors 2|, 22, 25 and 21 in the same manner as control station 8.

What is claimed is:

1. In a communication system, a conference circuit arrangement comprising a controlling station, a conference circuit and a plurality of subordinate stations, means under control of said controlling station for simultaneously calling all of said subordinate stations, and means responsive to said last means for superimposing a warning tone on said conference circuit.

2. In a communication system, a conference circuit arrangement comprising a controlling station, a conference circuit and a plurality of subordinate stations, means under control of said controlling station for simultaneously calling all of said subordinate stations, means responsive to said last means for superimposing a warning tone on said conference circuit, and means at said controlling station for removing said warning tone from said conference circuit.

3. In a communication system, a conference circuit arrangement comprising a controlling station having conventional switchhook facilities, a conference circuit stations, means under control of said controlling station for simultaneously calling all of said subordinate stations, means responsive to said last means for superimposing a warning tone on said conference circuit and means responsive to a momentary switchhook operation at said controlling station for removing said warning tone from said conference circuit.

4. In a communication system, a conference circuit arrangement comprising a controlling station, a conference circuit and a plurality of subordinate stations, a manually operated key at said controlling station for connecting said controlling station to said conference circuit, a manually operated ringing key at said controlling station effective only during the operation of said first key for simultaneously calling all of said subordinate stations, means responsive to said ringing key for superimposing a warning tone on said conference circuit, and means under control of the operator at said controlling station for removing said warning tone from said conference circuit.

5. In a communication system, a conference circuit arrangement comprising a controlling station, a conference circuit and a plurality of subordinate stations, a manually operated key at said controlling station for simultaneously calling all of said subordinate stations, a first relay responsive to the connection of any one or more of said stations to said conference circuit, a source of warning tone, a second relay responsive to the operation of said key and means for locking said second relay in operated position under control of said first relay, means controlled by said second relay for connecting said source of Warning tone to said conference circuit, a third relay responsive to momentary interruption of the connection between said controlling station and said conference circuit for disconnecting said source of warning tone from said conference circuit and means for locking said third relay in operated position under control of said first relay.

LAWRENCE H. ALLEN.

and a plurality of subordinate 

